Habitat Geometry Research Articles

Unraveling the unknown: Adaptive spatial planning to enhance climate resilience for the endangered Swamp Grass-babbler (Laticilla cinerascens) with habitat connectivity and complexity approach

The endangered and poorly known Swamp Grass-babbler, Laticilla cinerascens (Passeriformes: Pellorneidae), confronts critical threats and vulnerability due to its specific habitat requirements and restricted populations in the northeastern region of the Indian Subcontinent. This study investigates the distribution of the species, habitat quality, geometry and shape complexity of connectivity among the protected areas (PAs), and responses to climate change in Northeast India under different climate change pathways by utilizing ensemble distribution models, and ecological metrics. From the total distribution extent (1,42,000 km2), approximately 9366 km2 (6.59 %) is identified as the suitable habitat for this threatened species. Historically centered around Dibru Saikhowa National Park (DSNP), the species faced a drastic decline due to anthropogenic activities and alteration in land use and lover cover. The study also reveals a significant decline in suitable habitat for L. cinerascens in future climate scenarios, with alarming reductions under SSP126 (>10 % in the timeframe 2041–2060 and > 30 % from 2061 to 2080), SSP245 (>90 % in both time periods), and SSP585 (>90 % in both timeframes) from the present scenario. At present, DSNP has the most suitable habitat within the distribution range but is projected to decline (>90 %) under more severe climate change scenarios, as observed in other PAs. Landscape fragmentation analysis indicates a shift in habitat geometry, highlighting the intricate impact of climate change. It predicts a substantial 343 % increase (in the SSP126) in small habitat patches in the future. Connectivity analysis among PAs shows a significant shift, with a decline exceeding 20 %. The analysis of shape complexity and connectivity geometry reveals a significant increase of over 220 % in the fragmentation of connectivity among PAs between 2061 and 2080 under the SSP585 climate change scenario compared to the present conditions. The study underscores the urgent need for conservation actions, emphasizing the complex interplay of climate change, habitat suitability, and fragmentation. Prioritizing PAs with suitable habitats and assessing their connectivity is crucial. Adaptive management strategies are essential to address ongoing environmental changes and safeguard biodiversity. Future research in critical areas is needed to establish long-term monitoring programs to lead/extend effective conservation strategies.

Habitat geometry rather than visual acuity limits the visibility of a ground-nesting bird's clutch to terrestrial predators.

The nests of ground-nesting birds rely heavily on camouflage for their survival, and predation risk, often linked to ecological changes from human activity, is a major source of mortality. Numerous ground-nesting bird populations are in decline, so understanding the effects of camouflage on their nesting behavior is relevant to their conservation concerns. Habitat three-dimensional (3D) geometry, together with predator visual abilities, viewing distance, and viewing angle, determine whether a nest is either visible, occluded, or too far away to detect. While this link is intuitive, few studies have investigated how fine-scale geometry is likely to help defend nests from different predator guilds. We quantified nest visibility based on 3D occlusion, camouflage, and predator visual modeling in northern lapwings, Vanellus vanellus, on different land management regimes. Lapwings selected local backgrounds that had a higher 3D complexity at a spatial scale greater than their entire clutches compared to local control sites. Importantly, our findings show that habitat geometry-rather than predator visual acuity-restricts nest visibility for terrestrial predators and that their field habitats, perceived by humans as open, are functionally closed with respect to a terrestrial predator searching for nests on the ground. Taken together with lapwings' careful nest site selection, our findings highlight the importance of considering habitat geometry for understanding the evolutionary ecology and management of conservation sites for ground-nesting birds.

Origami-Inspired Deployable Space Habitats

Origami is increasingly used as a source of inspiration in a wide variety of disciplines. In this project, we explore cylindrical origami structures, referred to as “origami bellows”, as novel geometries for orbital space habitats. The dimensions of space habitats are limited by the tight mass and volume constraints imposed by launcher payload fairings. Future deployable habitats based on foldable origami bellows have the potential to achieve large volumes when deployed, while being capable of compacting to smaller stowed configurations for launch. To assess the feasibility of such habitat designs, the deployment performance of a selection of bellows was investigated. Bellows formed from Kresling and Miura-ori patterns were considered; both expand axially, but Miura-ori patterns experience an additional radial expansion. Our scope was also limited to patterns which are stable in both the stowed and deployed configurations. Habitats were judged on their internal and effective volume expansions; the latter being adjusted to account for the practicalities of operating within a complex habitat geometry. We find that significant internal and effective volume expansions are achievable, particularly for Miura-ori geometries. Nonetheless, we make the argument for Kresling patterns as a more practical option due to their simpler geometries, despite smaller volume expansions. We find our Kresling geometries to have effective volumes between 2.5 - 3.6 times greater than a conventional habitat launched in a fairing of equal volume. Our work shows that origami-based designs do indeed have potential to greatly outperform current space habitat designs. Keywords: Origami Bellows, Space Habitats, Deployable Structures

Habitat geometry in artificial microstructure affects bacterial and fungal growth, interactions, and substrate degradation

Microhabitat conditions determine the magnitude and speed of microbial processes but have been challenging to investigate. In this study we used microfluidic devices to determine the effect of the spatial distortion of a pore space on fungal and bacterial growth, interactions, and substrate degradation. The devices contained channels differing in bending angles and order. Sharper angles reduced fungal and bacterial biomass, especially when angles were repeated in the same direction. Substrate degradation was only decreased by sharper angles when fungi and bacteria were grown together. Investigation at the cellular scale suggests that this was caused by fungal habitat modification, since hyphae branched in sharp and repeated turns, blocking the dispersal of bacteria and the substrate. Our results demonstrate how the geometry of microstructures can influence microbial activity. This can be transferable to soil pore spaces, where spatial occlusion and microbial feedback on microstructures is thought to explain organic matter stabilization.

Nesting habitat and comb geometry of stingless bee Tetragonula bengalensis Cameron in west Bengal

A detailed survey was carried out at Purulia and Bankura districts of West Bengal to study the nesting habitat and comb geometry of stingless bee Tetragonula bengalensis Cameron. A total of 55 colonies were found to nest in different habitats, out of which 31 colonies were studied. Among them eleven colonies were found in tree nesting habitat and 20 in wall nesting. A colony nested in wall cavity at Bankura district was found to build their nest in that of swarmed wasp. The tree and wall nested colonies were observed having the mean height of 179.57, 173.25 and 99.71, 79.15 cm in the two respective districts. The mean dimensions of cavity and entrance tube nested in tree cavities of both the districts were 60.57 × 22.29 cm; 4.21 × 2.90 mm, and 35 × 17.75 cm; 3.75 × 3.5 mm; whereas for wall nested colonies it was 21.21 × 30.00 cm, 3.90 × 3.71 mm; and 20.87 × 28.69 cm, 3.98 × 3.60 mm, respectively. The brood cells, honey and pollen pots were brown to dark brown, oval and, arranged in clusters. The mean dimensions of brood cells, pollen and honey pots in tree nested combs were 2.26 × 1.66, 7.42 × 5.18, 7.60 × 4.77 and 2.26 × 2.00, 7.44 × 5.16, 7.80 × 4.99 mm; while for wall nested combs it was 2.28 × 1.57, 7.44 × 4.99, 7.57 × 4.71 and 2.13 × 1.77, 7.30 × 4.85, 7.77 × 4.65 mm in length and width, respectively.

Learning relationships between bat habitats and biosonar behavior

Echolocating bats are known to adapt their biosonar behaviors according to their surroundings. Vespertilionid bats, for example, adapt their pulse duration and bandwidth as a function of their proximity to foliage. However, these relationships have been based on mostly qualitative observations so far. More powerful methods that are capable of handling large quantitative datasets could produce further and more detailed insights. In the current work, aligned multimodal datasets have been gathered to address this challenge: habitat geometry (laser scans), acoustic scene (biomimetic active sonar system), bat flight trajectories (infrared camera array), and biosonar behavior (microphone array). Machine learning approaches can then be used to analyze relationships between the components of these multimodal datasets. To do this, representations of the bat’s surroundings that are suitable for biosonar problems have been developed, for example a probability density function of the angles and distances from the laser scanned points of a habitat model relative to the bat’s position and orientation. These representations will serve as inputs to machine learning algorithms that can predict the quantitative features of the bat’s biosonar behavior. This research could lead to a better understanding of bat pulse adaptation and also aid in developing biomimetic sonar navigation systems.Echolocating bats are known to adapt their biosonar behaviors according to their surroundings. Vespertilionid bats, for example, adapt their pulse duration and bandwidth as a function of their proximity to foliage. However, these relationships have been based on mostly qualitative observations so far. More powerful methods that are capable of handling large quantitative datasets could produce further and more detailed insights. In the current work, aligned multimodal datasets have been gathered to address this challenge: habitat geometry (laser scans), acoustic scene (biomimetic active sonar system), bat flight trajectories (infrared camera array), and biosonar behavior (microphone array). Machine learning approaches can then be used to analyze relationships between the components of these multimodal datasets. To do this, representations of the bat’s surroundings that are suitable for biosonar problems have been developed, for example a probability density function of the angles and distances from the las...

Modeling metabolic networks of individual bacterial agents in heterogeneous and dynamic soil habitats (IndiMeSH).

Natural soil is characterized as a complex habitat with patchy hydrated islands and spatially variable nutrients that is in a constant state of change due to wetting-drying dynamics. Soil microbial activity is often concentrated in sparsely distributed hotspots that contribute disproportionally to macroscopic biogeochemical nutrient cycling and greenhouse gas emissions. The mechanistic representation of such dynamic hotspots requires new modeling approaches capable of representing the interplay between dynamic local conditions and the versatile microbial metabolic adaptations. We have developed IndiMeSH (Individual-based Metabolic network model for Soil Habitats) as a spatially explicit model for the physical and chemical microenvironments of soil, combined with an individual-based representation of bacterial motility and growth using adaptive metabolic networks. The model uses angular pore networks and a physically based description of the aqueous phase as a backbone for nutrient diffusion and bacterial dispersal combined with dynamic flux balance analysis to calculate growth rates depending on local nutrient conditions. To maximize computational efficiency, reduced scale metabolic networks are used for the simulation scenarios and evaluated strategically to the genome scale model. IndiMeSH was compared to a well-established population-based spatiotemporal metabolic network model (COMETS) and to experimental data of bacterial spatial organization in pore networks mimicking soil aggregates. IndiMeSH was then used to strategically study dynamic response of a bacterial community to abrupt environmental perturbations and the influence of habitat geometry and hydration conditions. Results illustrate that IndiMeSH is capable of representing trophic interactions among bacterial species, predicting the spatial organization and segregation of bacterial populations due to oxygen and carbon gradients, and provides insights into dynamic community responses as a consequence of environmental changes. The modular design of IndiMeSH and its implementation are adaptable, allowing it to represent a wide variety of experimental and in silico microbial systems.

My branch is your branch: Talar morphology correlates with relative substrate size in platyrrhines at Tiputini Biodiversity Station, Ecuador

Given that most species of primates are predominantly arboreal, maintaining the ability to move among branches of varying sizes has presumably been a common selective force in primate evolution. However, empirical evaluations of the relationships between morphological variation and characteristics of substrate geometry, such as substrate diameter relative to an animal's body mass, have been limited by the lack of quantified substrate usage in the wild. Here we use recently published quantitative data to assess the relationships between relative substrate size and talar morphology in nine New World monkey species at the Tiputini Biodiversity Station, Ecuador. Within this sample, both fibular facet angle (the angle between the fibular facet and the trochlear rims) and body-mass-standardized area of the medial tibial facet decrease as average and maximum relative substrate size increases. Correlations between medial tibial facet area and relative substrate size are driven by the inclusion of callitrichids in this sample. Nevertheless, these findings strengthen the hypothesis that variation in fibular facet orientation and medial tibial facet area are functionally correlated with habitual degrees of pedal inversion. They also strengthen the notion that evolutionarily changing body mass could impact habitat geometry experienced by a lineage and thereby substantially impact major trends in primate morphological evolution. This study highlights the importance of empirical data on substrate use in living primates for inferring functional and evolutionary implications of morphological variation.

From habitat geometry to ecosystem functions in marine mussel beds

From habitat geometry to ecosystem functions in marine mussel beds

Metapopulation stability in branching river networks

Intraspecific population diversity (specifically, spatial asynchrony of population dynamics) is an essential component of metapopulation stability and persistence in nature. In 2D systems, theory predicts that metapopulation stability should increase with ecosystem size (or habitat network size): Larger ecosystems will harbor more diverse subpopulations with more stable aggregate dynamics. However, current theories developed in simplified landscapes may be inadequate to predict emergent properties of branching ecosystems, an overlooked but widespread habitat geometry. Here, we combine theory and analyses of a unique long-term dataset to show that a scale-invariant characteristic of fractal river networks, branching complexity (measured as branching probability), stabilizes watershed metapopulations. In riverine systems, each branch (i.e., tributary) exhibits distinctive ecological dynamics, and confluences serve as "merging" points of those branches. Hence, increased levels of branching complexity should confer a greater likelihood of integrating asynchronous dynamics over the landscape. We theoretically revealed that the stabilizing effect of branching complexity is a consequence of purely probabilistic processes in natural conditions, where within-branch synchrony exceeds among-branch synchrony. Contrary to current theories developed in 2D systems, metapopulation size (a variable closely related to ecosystem size) had vague effects on metapopulation stability. These theoretical predictions were supported by 18-y observations of fish populations across 31 watersheds: Our cross-watershed comparisons revealed consistent stabilizing effects of branching complexity on metapopulations of very different riverine fishes. A strong association between branching complexity and metapopulation stability is likely to be a pervasive feature of branching networks that strongly affects species persistence during rapid environmental changes.

Correlates of ecological-niche diversity and extinction risk of amphibians in China under climate change

In the present study, we measured spatiotemporal properties of ecological niches of amphibians in China and tested the relative importance of various niche-diversity metrics for explaining the evolutionary distinctiveness-weighted extinction risk (EDGE) of amphibian species. We applied the hierarchical partitioning technique on the phylogenetically independent contrasts of the niche covariates and EDGE of amphibians, for the purpose of removing the influence of evolutionary inertia among species. As a comparison, phylogenetic least-square general regression (PLGS) was also conducted. The results showed that EDGE was high for those amphibian species of China identified as Critically Endangered or Endangered on the IUCN Red List. Niche fragmentation dimension (NFD) and niche position (NP) were the top two predictors across partial correlation analyses, hierarchical variation partitioning, PLGS and multiple regression analyses. Most temporal niche properties were not significantly associated with the EDGE index of amphibians. Variation partitioning analysis showed that the spatial component of niche measures explained the largest proportion of total variation in EDGE (~31%), whereas the temporal component of niche properties explained ~8% of the variation. The significantly negative role of NFD and extinction risk of amphibians in China may be attributed to a reduced rescue effect, habitat geometry, and local extinction in species with large and continuous distributional ranges.

Tsetse Control and the Elimination of Gambian Sleeping Sickness.

Tsetse Control and the Elimination of Gambian Sleeping Sickness.

Habitat geometry, a step toward general bird community assembly rules in mature forests

Community ecology has often been criticized because it seldom defines general rules that can be exported outside of the studied system. Although much progress has been achieved by studying functional traits instead of species identities per se, environmental gradients defined in terms of local resources can be measured only on a subset of ecosystems and, thus, are not deemed general. Here, we used state-of-the-art statistical approaches for modeling the interaction between species functional traits (body size, feeding substrate) and habitat geometry (object size, shape and color; packing, layering and texturing), such as to derive general assembly rules for bird communities in an even-aged mature forest (La Mauricie National Park, Québec, Canada). Our results show that habitat geometry filters the species pool through its interaction with bird body size and feeding substrate, both at the species, and even more so at the community level. We found comparable assembly rules using only photographic (image-based) descriptors of habitat geometry, thus providing forest managers with a fast, reliable, standardized and cost-effective protocol for characterizing forest stands. Because bird functional groups respond differently to environmental gradients, we conclude that mature forest should be managed to preserve a spatial mosaic of successional states.

Explaining the host-finding behavior of blood-sucking insects: computerized simulation of the effects of habitat geometry on tsetse fly movement.

BackgroundMale and female tsetse flies feed exclusively on vertebrate blood. While doing so they can transmit the diseases of sleeping sickness in humans and nagana in domestic stock. Knowledge of the host-orientated behavior of tsetse is important in designing bait methods of sampling and controlling the flies, and in understanding the epidemiology of the diseases. For this we must explain several puzzling distinctions in the behavior of the different sexes and species of tsetse. For example, why is it that the species occupying savannahs, unlike those of riverine habitats, appear strongly responsive to odor, rely mainly on large hosts, are repelled by humans, and are often shy of alighting on baits?Methodology/Principal FindingsA deterministic model that simulated fly mobility and host-finding success suggested that the behavioral distinctions between riverine, savannah and forest tsetse are due largely to habitat size and shape, and the extent to which dense bushes limit occupiable space within the habitats. These factors seemed effective primarily because they affect the daily displacement of tsetse, reducing it by up to ∼70%. Sex differences in behavior are explicable by females being larger and more mobile than males.Conclusion/SignificanceHabitat geometry and fly size provide a framework that can unify much of the behavior of all sexes and species of tsetse everywhere. The general expectation is that relatively immobile insects in restricted habitats tend to be less responsive to host odors and more catholic in their diet. This has profound implications for the optimization of bait technology for tsetse, mosquitoes, black flies and tabanids, and for the epidemiology of the diseases they transmit.

Tactical Predictions of Shoreline Oiling Probability via Machine Learning Models and Satellite-Derived Surface Oil Analysis Products

ABSTRACT For significant oil spills in remote areas with complex shoreline geometry, apportioning Shoreline Cleanup Assessment Technique (SCAT) survey effort is a complicated and difficult task. Aerial surveys are often used to select shoreline areas for ground survey after an initial prioritization based upon anecdotal reports or trajectory models, but aerial observers may have difficulty locating cryptic surface shoreline oiling in vegetated or other complex environments. In dynamic beach environments, stranded shoreline oiling may be rapidly buried, making aerial observation difficult. A machine learning-based model is presented for estimating shoreline oiling probabilities via satellite-derived surface oil analysis products, wind summary data, and shoreline habitat type and geometry data. These inputs are increasingly available at spatial and temporal scales sufficient for tactical use, enabling model predictions to be generated within hours after satellite remote sensing products are available. The model was constructed using SCAT data from the Deepwater Horizon oil spill, satellite-derived surface oil analysis products generated during the spill by NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) using a variety of satellite platforms of opportunity, and available shoreline geometry, character, and other preexisting data. The model involves the generation of set of spatial indices of relative over-water proximity of surface oil slicks based upon the satellite-derived analysis products. The model then uses boosted regression trees (BRT), a flexible and relatively recently developed modeling methodology, to generate calibrated estimates of probability of subsequent shoreline oiling based upon these indices, wind climatological data over the time period of interest, and other shoreline data. The model can be implemented via data preparation in any Geographic Information System (GIS) software coupled with the open-source statistical computing language, R. The model is entirely probabilistic and makes no attempt to reproduce the physics of oil moving through the environment, as do trajectory models. It is best used in concert with such models to make estimates at different spatial scales, or when time and data requirements make implementation of fine-scale trajectory modeling impractical for tactical use. The details of model development implementation and assessments of model performance and limitations are presented.

Habitat geometry does not affect levels of extrapair paternity in an extremely unfaithful fairy-wren

Density of potential mates has often been proposed to explain the enormous variation in extrapair paternity. However, density is often confounded by other ecological factors that might affect extrapair paternity in their own way. Furthermore, extrapair mating shows strong phylogenetic inertia, making both meaningful intra- and interspecific comparisons difficult. An extreme way to change density is through habitat fragmentation that reduces connectivity between territories. Recently, habitat connectivity was hypothesized to explain the surprising discovery of a virtually monogamous species among the world’s most unfaithful bird genus. The monogamous Malurus coronatus lives in narrow riparian strips that limit contact with neighbors to both extreme ends of territories, whereas Malurus species with high levels of extragroup paternity typically live in high-connected habitat in which they are surrounded by neighbors. Here, we test the habitat geometry hypothesis by comparing levels of extragroup paternity of Malurus elegans living in fragmented low-connected habitat and in high-connected habitat. We found that M. elegans does not have lower levels of extragroup paternity in low-connected habitat (68%) than in high-connected habitat (56% of offspring), indicating that connectivity does not limit opportunities for extragroup paternity. Furthermore, there was no evidence that females in low-connected habitat gained extragroup paternity further away or from less sires or that they were more likely to be closely related to their social mate. We conclude that behavioral plasticity in response to density-dependent cost and benefits of mating behavior does not explain intrageneric variation in extragroup paternity in Malurus. Furthermore, habitat fragmentation may not strongly affect inbreeding risk in this species.

Habitat Quality and Geometry Affect Patch Occupancy of Two Orthopteran Species

Impacts of habitat loss and fragmentation on distribution and population size of many taxa are well established. In contrast, less is known about the role of within-patch habitat quality for the spatial dynamics of species, even though within-patch habitat quality may substantially influence the dynamics of population networks. We studied occurrence patterns of two Orthopteran species in relation to size, isolation and quality of habitat patches in an intensively managed agricultural landscape (16.65 km2) in the Swiss lowland. Occurrence of field crickets (Gryllus campestris) was positively related to patch size and negatively to the distance to the nearest occupied patch, two measures of patch geometry. Moreover, field crickets were more likely to occur in extensively managed meadows, meadows used at low intensity and meadows dominated by Poa pratensis, three measures of patch quality. Occurrence of the large gold grasshopper (Chrysochraon dispar) was negatively related to two measures of patch geometry, distance to the nearest occupied patch and perimeter index (ratio of perimeter length to patch area). Further, large gold grasshoppers were more likely to occupy patches close to water and patches with vegetation left uncut over winter, two measures of patch quality. Finally, examination of patch occupancy dynamics of field crickets revealed that patches colonized in 2009 and patches occupied in both 2005 and 2009 were larger, better connected and of other quality than patches remaining unoccupied and patches from which the species disappeared. The strong relationships between Orthopteran occurrence and aspects of patch geometry found in this study support the “area-and-isolation paradigm”. Additionally, our study reveals the importance of patch quality for occurrence patterns of both species, and for patch occupancy dynamics in the field cricket. An increased understanding of patch occupancy patterns may be gained if inference is based on variables related to both habitat geometry and quality.

Local and Regional Determinants of Colonisation-Extinction Dynamics of a Riparian Mainland-Island Root Vole Metapopulation

The role of local habitat geometry (habitat area and isolation) in predicting species distribution has become an increasingly more important issue, because habitat loss and fragmentation cause species range contraction and extinction. However, it has also become clear that other factors, in particular regional factors (environmental stochasticity and regional population dynamics), should be taken into account when predicting colonisation and extinction. In a live trapping study of a mainland-island metapopulation of the root vole (Microtus oeconomus) we found extensive occupancy dynamics across 15 riparian islands, but yet an overall balance between colonisation and extinction over 4 years. The 54 live trapping surveys conducted over 13 seasons revealed imperfect detection and proxies of population density had to be included in robust design, multi-season occupancy models to achieve unbiased rate estimates. Island colonisation probability was parsimoniously predicted by the multi-annual density fluctuations of the regional mainland population and local island habitat quality, while extinction probability was predicted by island population density and the level of the recent flooding events (the latter being the main regionalized disturbance regime in the study system). Island size and isolation had no additional predictive power and thus such local geometric habitat characteristics may be overrated as predictors of vole habitat occupancy relative to measures of local habitat quality. Our results suggest also that dynamic features of the larger region and/or the metapopulation as a whole, owing to spatially correlated environmental stochasticity and/or biotic interactions, may rule the colonisation – extinction dynamics of boreal vole metapopulations. Due to high capacities for dispersal and habitat tracking voles originating from large source populations can rapidly colonise remote and small high quality habitat patches and re-establish populations that have gone extinct due to demographic (small population size) and environmental stochasticity (e.g. extreme climate events).

Visual habitat geometry predicts relative morph abundance in the colour-polymorphic ornate rainbowfish

During colour signalling in aquatic environments, the colour of the ambient light, the background against which signals are viewed and signal transmission through the environment can all have profound impacts on the efficacy of a given signal. In colour-polymorphic species, where alternative morphs persist owing to a balance in the natural and sexual selection for each, changes to the visual context can have large effects on the local success and relative abundance of competing phenotypes. The ornate rainbowfish, Rhadinocentrus ornatus, is composed of populations that vary in the relative frequency of red and blue individuals, and inhabit sites that vary in water transmittance from clear (white) to heavily tannin-stained (red-shifted). Using spectroradiometry, we measured the downwelling and sidewelling irradiance, bank radiance and water transmittance of 10 R. ornatus habitats. We found that the relative local abundance of each morph was predicted not by water transmittance but by chromatic differences between the vertical (downwelling light) and horizontal (bank colour) components of the habitat. This visual habitat geometry should increase contrast between the colour signal and background, with large potential to influence the strength of natural and sexual selection in this system.

Metapopulation dynamics of the bog fritillary butterfly: experimental changes in habitat quality induced negative density-dependent dispersal

Habitat quality and habitat geometry are two crucial factors driving metapopulation dynamics. However, their intricacy has prevented so far a reliable test of their relative impact on local population dynamics and persistence. Here we report on a long-term study in which we manipulated habitat quality within a butterfly metapopulation, whereas habitat geometry was kept constant. The treatment consisted in lowering the quality of certain habitat patches while others were kept untreated, using the same spatial design over years. The effect of the treatment on metapopulation dynamics was assessed by comparing residence probability and dispersal rates within the same habitat network on 11 and 6 independent butterfly generations before and after treatment, respectively. Results showed that the experimental decrease in habitat quality generated significantly higher emigration rates from treated patches. This increase was associated with a significant decrease in dispersal rates out of untreated patches, and a significant higher residence probability in these patches. The direct relation between lower habitat quality and higher dispersal propensity in treated patches was expected. However, the lower dispersal from untreated patches after treatment was opposite to the expectation of positive density dependent dispersal generally observed in butterflies. Such negative density-dependent dispersal would allow a rapid fine-tuning of dispersal rates to changes in habitat quality, particularly when the spatial autocorrelation of the environmental is low. Accordingly,dispersal would promote an ideal free distribution of individuals in the landscape according to their fitness expectation.